The present disclosure relates to an image reading device for reading an image of an object, an image forming apparatus, and a recording medium.
A user may use an image reading device for reading not only an image on paper but also a three-dimensional object including a glossy portion (hereinafter referred to as the “glossy object”). The glossy object is, for example, a cash card (having a portion of carved letters or a portion coated in silver or gold), clothing (having buttons or a decorated portion), and jewelry.
When a glossy object is read by an image reading device, strong light mirror reflected on the glossy object enters an image sensor (a photoelectric conversion element). Accordingly, in an image reading device in which the light amount of a light source is adjusted for reading an image on paper, an image sensor receives light having an amount beyond the saturation light exposure of the image sensor. This results in charge exceeding a charge capacity storable in one pixel of the image sensor, and hence the charge overflows to an adjacent pixel, which causes an abnormality in the read image of the glossy object.
In an image reading device disclosed in Patent Document 1, if an image signal at a level beyond a precedently set value is output from an image sensor while reading a glossy object after reading a white reference plate, charge storage time for each pixel of the image sensor is shortened. With the charge storage time thus shortened, the white reference plate is read again, and the glossy object is then read again. As a result, the overflow of the charge in each pixel of the image sensor can be suppressed in this image reading device.